The present invention relates to concrete-crushing pincers.
Concrete-crushing pincers are utilized for demolishing structures made of reinforced concrete. In this connection, it is particularly desirable that through the pincer movement of the concrete-crushing pincers, the concrete is crushed, on the one hand, and the reinforcing iron is cut in the same course of movement, on the other hand. The demolition material thus broken up can thereby be fed for further processing to, for example, a breaker in which separation of concrete and metal takes place, without any additional working operation, such as severing reinforcing iron with a cutting torch if it is not optimally cut by the concrete-crushing pincers.
Such concrete-crushing pincers are known. Thus, for example, such concrete-crushing pincers are shown in U.S. Pat. No. 5,183,216. These concrete-crushing pincers also comprise, besides the crushing teeth, cutting elements which are held in rectangular-shaped recesses. During cutting of the reinforcing irons, these cutting elements are subjected to high stresses. Areas of the rectangular-shaped recesses may thereby be excessively stressed, which may result in deformation. This leads to damage of the recesses, which must be eliminated by expensive repair work.
In European Patent No. 0 770 164, concrete-crushing pincers are shown which have two pincer jaws, each of which is provided with concrete-crushing sectors and cutting edges. The concrete-crushing sectors project over the cutting edges, to avoid crushing of the concrete by the cutting edges which are provided for cutting the reinforcing iron and should therefore have a relatively sharp edge. The concrete-crushing edge and the cutting edge are rotary, i.e., in order to be able to cut the reinforcing iron optimally, the concrete-crushing edge must not project too far over the cutting edge. The cutting edge is also highly stressed by the crushing of the concrete, which may result in heavy wear and tear and expresses itself in decreasing cutting quality for the reinforcing iron.
Since the cutting edges are exposed to high forces of traction and compression during cutting of the reinforcing iron, the respective cutting elements must be optimally joined to the respective pincer jaw. In these previously described concrete-crushing pincers, this is achieved in that the material forming the cutting edge is welded onto the pincer jaw. This has the drawback, however, that in case of wear of this cutting edge, new material must be welded on, which usually takes place in a workshop, whereby the pincers are not in operation for some time, and long down-times occur. Furthermore, additional material cannot be welded onto the pincer jaw as often as desired since structural modifications of the material occur through the heating, whereby the strength of this material and hence the connection between welded-on material and pincer jaw is no longer optimal and the additional material may break off.
A task of the present invention now consists in creating concrete-crushing pincers in which the renewal of the cutting edges may be carried out without requiring long stoppage times, and in which optimum crushing of the concrete is achieved.
According to the invention, the solution of this task takes place by means of the following features. Concrete-crushing pincers having a first pincer jaw and a second pincer jaw are connected to one another via a joint and are movable via hydraulic cylinders about a swivel axis formed by the joint from an open position into a closed position. The first pincer jaw is formed by a frame body in which first concrete-crushing sectors and first cutting sectors are disposed. The second pincer jaw is formed by a body on which second concrete-crushing sectors and second cutting sectors are disposed, which, during closing of the concrete-crushing pincers, while the second pincer jaw penetrates into the frame body of the first pincer jaw, cooperate with the first concrete-crushing sectors and the first cutting sectors of the first pincer jaw. The first and the second cutting sectors are each formed of first and second cutting elements, respectively, which are inserted in receiving pockets affixed in the first pincer jaw and the second pincer jaw and are detachably fastened therein, such that the first cutting elements are fastened to the lateral areas of the first pincer jaw and the second pincer jaw. The first cutting elements are each formed of a block provided with a bend, the convex surface of which rests in the receiving pocket provided with a corresponding support surface, and the concave surface of which, with the lateral surfaces lying in a plane standing perpendicular to the swivel axis, each form a cutting edge.
By allowing the cutting elements of the concrete-crushing pincers to be exchanged, which can practically be undertaken at the place of use of these concrete-crushing pincers, long stoppage times are avoided.
In this connection, first cutting elements, each formed of a block provided with a bend, are fastened to the lateral areas of the first pincer jaw and of the second pincer jaw. Moreover, their convex surface rests in the receiving pocket of the pincer jaw provided with a corresponding support surface, whereas their concave surfaces each form a cutting edge with the lateral surfaces lying in a plane standing perpendicular to the swivel axis. Besides the advantage that these individual blocks can be very quickly replaced, it is thereby also achieved that the absorption of the forces during cutting of the reinforcing iron and their transmission to the pincer jaws can take place in an optimal manner.
A further advantageous arrangement of the invention includes a guide rib that is affixed to the convex surface of the previously described block, which guide rib is aligned longitudinally to the convex surface and runs centrally, the respective support surface of the receiving pocket being equipped with a groove corresponding to the guide rib, in which groove the guide rib engages when the block is inserted in the pincer jaw. By means of this device, the block is held optimally in the receiving pocket of the respective pincer jaw.
A further advantageous arrangement of the invention includes elements that are affixed to the end regions of the support surfaces of the receiving pockets, which elements are provided with stop surfaces against which the end faces of the blocks rest when inserted in the receiving pockets. By this means, these blocks are optimally held in the receiving pockets. Since the blocks themselves are not connected to the pincer jaw, for instance with screws, no excessive stress peaks arise through the forces occurring during the cutting operation, which stress peaks might for instance lead to breaking of the screws, since the forces can be optimally led over into the pincer jaw.
Advantageously, first cutting elements formed by the blocks are provided, disposed two at a time in a row on each lateral area of the pincer jaws, which elements are held in the receiving pockets by teeth screwable onto the pincer jaw. The tips of the teeth project over the cutting edges of the cutting elements, whereby the crushing of the concrete is at least initiated by these teeth, and the cutting edges are thus spared.
A further advantageous arrangement of the invention includes the bend of the block forming the cutting elements is arcuate, whereby the bearing surface is optimal, and the fabrication of the blocks and the receiving pockets is simplified. The concave surface of the blocks situated between the two cutting edges has a curvature, and the wedge angle of the cutting edge becomes greater than 90xc2x0. During cutting of the reinforcing iron, the latter thus rests first upon the curvature, it is pressed straight before the cutting edges engage, whereby again the cutting edges are protected. Through the symmetrical arrangement of these blocks, this block can be rotated in the receiving pocket in such a way that one of the two cutting edges is in use each time, whereby the material is optimally utilized.
A further advantageous arrangement of the invention includes a plate forming the second cutting element that is affixed to the end-face area of the first and the second pincer jaw, respectively, which plate rests with one lateral area each on a corresponding support surface of the receiving pocket, and optimum transmission of force to the pincer jaw is thus achieved.
The rear side of this plate is supported against a wall, adjoining the support surface, of the first pincer jaw and the second pincer jaw, respectively, and is screwed to the latter. Thus this plate is also easily exchangeable.
Advantageously, the two lateral surfaces of the plate are provided with indentations and projections, along which the cutting edge runs. The plate may be inserted in the receiving pocket in such a way that either one or the other of the two cutting edges is in use. By this means, too, the material is optimally utilized.
A further advantageous arrangement of the invention includes the plate being disposed between the two front teeth of the first and/or second pincer jaw, respectively, with the tips of the teeth projecting over the cutting edge of the plate. The crushing of the concrete is thereby again at least initiated over the teeth, and the cutting edge of the plate is spared as a result.
In order that the concrete may be crushed optimally and the cutting edges of the cutting elements may be protected, additional teeth are affixed to the second pincer jaw, and these teeth are disposed between each of two teeth forming a pair and project over their tips. During demolishing of reinforced concrete, the area grasped by the pincers is first subjected to bending stress, and the concrete thus breaks more easily.
Advantageously, the teeth are disposed in the pincer jaws so that upon closing of the pincers, first the rear teeth come in contact with the portion of concrete to be broken off, and the concrete is crushed in this sector, and only thereafter do the front teeth engage. The crushing of the concrete thereby becomes easier.
An embodiment of the present invention is described in detail below, by way of example, with reference to the enclosed drawings.